Apparatus for actuating shutter blades or the like



United States Patent [72] inventor Hans-Ado Brandt Munich, Germany [21 Appl. No. 739,481

[22] Filed June 24, 1968 [45] Patented Dec. 8, 1970 [7 3] Assignee AGFA-Gevaert Aktiengesellschaft Leverkusen, Germany [3 2] Priority June 23, 1967 [3 3] Germany [54] APPARATUS FOR ACTUATING SHUTTER BLADES OR THE LIKE 15 Claims, 7 Drawing Figs.

[52] U.S. Cl 95/61, 353/88 [51] Int. Cl G03b 9/20 [50] Field ofSearch 95/53, 58, 59, 61, 63(lnquired); 353/88, 91, 92

[56] References Cited UNITED STATES PATENTS 2,226,245 12/1940 Kende 95/61 Primary ExaminerJohn M. Horan Assistant Examiner-Robert P. Greiner Att0rneyMichael S. Striker ABSTRACT: A shutter blade or a group of filters is moved across and away from the path of light in a camera or printer by a rotary member biased by two springs one of which acts upon the rotary member by way of a cam and follower assembly. The one spring dissipates energy during a first stage of movement of the rotary member to accelerate the latter, and stores energy during the next following stage to thus decelerate the rotary member, The other spring is stressed by a motor and biases the rotary member with a force which suffices to compensate for friction.

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HANS -ADO BRANDT APPARATUS FOR ACTUATING suurmn BLADES on THE LIKE BACKGROUND OF THE INVENTION The present invention relates to apparatus for driving movable parts, particularly for transmitting motion to shutter blades, color filters and analogous parts which must be moved into or away from the path of light in cameras, printers, copiers or analogous machines or apparatus.

Modern high-speed color printers employ shutters which must rapidly admit and/or terminate the admission of light to a photosensitive carrier. In certain conventional printers, the admission of light is terminated by shutting off the printing lamp; such procedure is unsatisfactory in modern color printers because the filament of the printing lamp continues to glow and to emit light which is in excess of the optimum amount of light determined by the exposure control of the printer. As a rule, such exposure control comprises photoelectric means which scans a negative and determines, with a high degree of accuracy, that amount of light which should reach the photosensitive carrier. The printing lamp normally continues to emit yellow and red light which 'is particularly undesirable in color printing because the thus emitted excess amounts of yellow and red light affect the color balance of prints. v

Certain other types of printers employ shutters which are operated by electromagnetic means. The shutter is opened by a spring because a relatively slow opening of the shutter cannot effect the quality of prints as long as the total amount of light is not excessive. The exposure control measures the amounts of light which are admitted by the thus opened shutter and energizes the electromagnet to effect rapid closing of the shutter when the latter completes the admission of an optimum amount of light. The electromagnet is normally energized in response to sudden discharge of a capacitor. In order to insure rapid closing of the shutter, the mass of moving parts must be small and such parts must cover. a relatively .short distance. Therefore, the blade or blades of the shutter in such printers are normally arranged to move across a restricted portion of the light path, i.e., across that portion where the cross-sectional area of the light beam is very small. Thus, the shutter must move its blade or blades across that portion of the light path which is closely adjacent to the image of the light source. On the other hand, and in order to obtain soft copying light, it is desirable to install the shutter in such a way that it can move its blade or blades across that portion of the light path (wherein the light beam has a large cross-sectional area. The same applies when the printing apparatus employs color filters. Energization of electromagnets which are strong enough to move a large filter or a large shutter blade consumes too much time. Furthermore, the operation of such printers is uneconomical because large amounts of kinetic energy must be destroyed by braking in order to rapidly arrest a bulky shutter blade or filter.

SUMMARY or THE INVENTION It is an object of the present invention to provide a novel and improved apparatus which can be employed to move shutter blades, filters, masks or analogous parts in an optical copying, printing or like machine.

Another object of the invention is to provide a motion transmitting apparatus for shutter blades, vanes, filters, masks or analogous parts and to construct and assemble the apparatus in such a way that the movable parts can be accelerated and decelerated at a controlled speed and with a minimum of wear and noise. a

A further object of the invention is to provide an apparatus which can move shutter blades, filters or like parts across the path of light in a region where the cross-sectional area of travelling light is relatively large and which can be used in combination with existing exposure controls to regulate, with a high degree of accuracy, the amounts of light which can reach a photosensitive carrier or the like.

A concomitant object of the invention is to provide an apparatus which is particularly suited for use in machines or instruments wherein the transmission of scene light or printing light must be terminated with a minimum of delay.

Still another object of the invention is to provide an apparatus which comprises a small number of simple parts, which occupies little room, and which can be utilized to transmit motion to a single part or to groups to two or more parts.

The improved apparatus comprises output means movable in synchronism with one or more movable parts between first and second positions, biasing means operatively connected with the output means and arranged to store a predetermined amount of energy in the first position of the output means, to accelerate the output means during a first stage of movement of output means from first position with attendant dissipation of at least some energy, and to store energy during the nextfollowing stage of movement of the output means from first position with attendant deceleration of the output means, and auxiliary drive means for urging the output means toward second position with a force which suffices to at least compensate forfriction which must be overcome by the output means during movement from first to second position.

The output means may comprise one or more rotary members which can be directly or indirectly coupled to one or more movable parts, and the biasing means may comprise a spring or weight. An energy transmitting unit of the output means (for example, a cam and follower assembly or a crank chain) transmits motion from the weight or spring to the rotary members during the first stage of movement of movable parts and causes the spring or weight to store energy during the next-following stage. The auxiliary drive means may comprise a spring which is stressed by a motor or the like to store a certain amount of energy which suffices to compensate for frictional losses during movement of rotary members from first to second position and for friction which must be overcome by the energy transmitting unit.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic elevational view of an apparatus which embodies one form of the present invention and which is employed to move a shutter blade between open and closed positions;

' FIG. 2 is a graph wherein the curves indicate the angular displacement and angular velocity of the shutter blade as a function of time;

FIG. 3 is an enlarged sectional view of a second apparatus which is similar to the apparatus of FIG. 1;

FIG. 4 is a view as seen in the direction of arrow IV in FIG. 3 and illustrates the shutter blade of the second apparatus in open position;

FIG. 5 illustrates the shutter blade of the second apparatus in closed position;

FIG. 6 is a schematic elevational view of a third apparatus which is utilized to transmit motion to three color filters; and

FIG. 7 is a similar schematic view of a fourth apparatus which transmits motion to two filters.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, there is shown a portion of an apparatus which can be used in aphotographic camera to control the amounts of scene light reaching an unexposed film frame or in an optical copying or printing machine to regulate the amounts of printing light which can reach a photosensitive sheet of printing paper or the like. The apparatus comprises an output unit which includes a shaft 1 supporting a rotary cam 2. The cam 2 is connected to and can transmit motion to one or more movable parts, for example, to a part corresponding to the shutter blade 18 shown in FIGS. 3 to 5. The motion transmitting connection between the cam 2 and the. movable part or parts may comprise a gear train (shown in FIG. 7) but it is equally possible to provide a rigid connection between the cam and the movable part or parts. In the latter instance, the movable part or parts can be mounted for rotation on the shaft 1. The earn 2 resembles a disc and is free to rotate on the shafi 1; it is provided with at least one pair of suitably configurated peripheral cam faces or flanks 2a, 2b and is engaged by a roller follower 3 which forms part of a output unit. The latter further includes an elongated lever or arm 4 which is fulcrumed at 6 and is connected with one end of a resilient biasing means here shown as a helical contraction spring 5. The other end of the spring is connected to a stationary member, not shown. The parts 2, 3 together constitute an energy transmitting means between the shutter blade and the spring 5.

The cam 2 is coaxial with and is rigidly secured to an index wheel 2A provided with a peripheral notch-2c which is angularly offset with reference to the cam faces 2a, 2b. In the angular position shown in FIG. 1, the notch 20 receives the tang of a pawl 7a which is turntable on a fixed pin 7b and is biased by a torsion spring 40 tending to urge the tang against the periphery of the wheel 2A. The pawl 7a constitutes the armature of an arresting or holding electromagnet 7 whosewinding is connected to the exposure control of the camera and is energizable to attract the pawl 7a against the opposition of the spring 40 to disengage the pawl from the wheel 2A and to thus permit clockwise rotation of the cam 2 under the action of the spring 5 and under the action of an auxiliary drive including a torsion spring 9 one end of which is fixed to the cam 2 and the other end of which is fixed to a worm wheel 9a.

The notch 2c can also receive the tang of a second pawl 8a which is biased by a torsion spring 400 so that it tends to bear against the index wheel 2A. The pawl 80 constitutes the annature of a second arresting or holding electromagnet 8 whose winding is also connected with the aforementioned exposure control. This exposure control may be of the type as disclosed,

for example, in German Pat. No. 972.704.

As stated before, the spring 9 forms part of an auxiliary drive which also includes the worm-wheel 9a, a worm 9b which meshes with the worm wheel 9a, a continuously or intermittently driven electric motor 10 which rotates the worm clockwise direction. The purpose of the auxiliary drive including the parts 9, 9a, 9b, 10, 37 is to compensate for losses which are due to friction arising when the earn 2 moves from first to second position as well as to compensate for frictional losses which develop when the lever 4 turns on the pivot 6, when the follower 3 rotates about its axis, and when the follower tracks the earn 2.

The configuration of the face on the cam 2 is such that the follower 3 can effect uniform acceleration of the cam when the tang of the pawl 7a is withdrawn from the notch 2c of the index wheel 2A, and that such acceleration is rapid but without undue wear on the energy transmitting parts 2 and 3.

The operation of the apparatus will be described with reference to FIG. 1 and with simultaneous reference to FIG. 2 wherein the time t (in thousandths of a second) is measured along the abscissa. The angular displacement or and the angular velocity at of the cam 2 are measured along the ordinate.

9b, and a friction clutch 37 which is installed between the output shaft of the motor 10 and the worm 9b. The worm wheel 9a is freely rotatable on the shaft 1. The purpose of the motor 10 is to maintain the spring 9 under a certain stress whereby the spring 9 assists the spring 5 in rapidly moving the cam 2 from the first or starting position shown in FIG. I to a second in which the spring 5 again stores at least as much energy as the first position of the cam.

When the cam 2 assumes the first position shown in FIG. 1, the notch 2c receives the tang of the pawl 7a and the electromagnet 7 is deenergized, i.e., the spring 40 is free to maintain the pawl 7a in blocking or arresting engagement with the index wheel 2A so that the cam 2 and the shutter blade connected therewith are at a standstill. The spring 5 stores a little less than a maximum amount of energy because the roller follower 3 is in engagement with the outermost end of thecarn face 2a so that it is located at less than maximum distance from the axis of the shaft 1. The position of the roller follower 3 at a maximum distance from the shaft 1 is indicated by phantorn lines as at 3"; the follower 3 assumes such position when it tracks the circular peripheral surface 2d of the cam 2. The spring 5 tends to move the roller follower 3 radially inwardly toward the axis of the shaft 1 and to thereby effect angular displacement of the earn 2 in a clockwise direction, as viewed in If the electromagnet 7 is energized to attract the pawl 7a, the cam 2 is caused to leave its first orstarting position not only under the action of the spring 9 but particularly under the action of spring 5 so that the cam rotates in a clockwise direction and is rapidly acceleratedwhile the follower 3 rolls along the cam face 20. The curve 38 of FIG. 2 illustrates that the cam 2 undergoes sudden acceleration within a few thousandths of a second. The accelerating action of the spring 5 is terminated when the roller follower 3 reaches the deep-- most zone of the recess bounded by cam faces 20, 2b (position 3' of FIG. 1); the cam 2 then attains its maximum angular speed and the face 2a assumes the position 2. The spring 9 continues to bias the cam 2 in a clockwise direction to compensate for aforementioned frictional losses.

The shutter blade which moves in synchronism with the cam 2 closes about percent of the light-admitting opening when the roller follower3 reaches the cam face 2b (point A on the curve 37 in FIG. 2). The kinetic energy of the rotating cam 2 is then transmitted to the spring 5 (in the position 5' of FIG. I) which stores energy while the follower 3 tracks the face 2b.

The shutter blade closes the light-admitting opening when the '2 (position 2" of the cam face 2b in FIG. 1). The total time required for closing of the shutter is 10 thousandths of a second.

When the roller follower 3 reaches the peripheral surface 2d of the cam 2 (position 3"), the spring 5 stores at least as much energy as when the tang of the pawl 7a enters the notch 20 of the index wheel 2A. The cam 2 continues to rotate in a clockwise direction due to the bias of torsion spring 9 which is stressed by the motor 10. The dimensioning of the spring 9 is such that energy stored in this spring before the pawl 70 releases the index wheel 2A suffices to compensate for afore-' mentioned frictional losses, for losses due to hysteresis, and to surface 2d, i. e. when the follower assumes the position 3". The spring 9 also compensates for the additional work required to move the roller follower 3 to the position 3", namely, to a position in which the roller follower is located at a maximum radial distance from the axis of the shaft 1, i.e., at a distance which exceeds the distance in the solid-line position of the follower.

The cam 2 is brought to a halt when the tang of the pawl 8a enters the notch 2c of the index wheel 2A. The follower 3 then engages the outermost end of a further face (not shown) of the cam 2, such further face corresponding to the cam face 20 but being angularly spaced from the outermost end of the face 2a by the same distance as that between the tangs of the pawls 7a,

8a. The next exposure is made in the same way as described- When the springs and 9 store maximum amounts of energy, the energy stored by spring 5 can'be three times the energy stored by spring 9. Y

The electromagnets 7, 8 may form part of an electric circuit similar to the one disclosed in U.S. Pat. No. 3,002,425.

As stated before, the index wheel 2A can be provided with several notches 2c, depending on the number of cam faces on the member 2.

The details of a shutter which embodies the present invention and utilizes the parts shown in FIG, 1 are illustrated in FIGS. 3 to 5. The shuttercomprises a base plate or main support 11 which ismounted in an optical copying machine so that it is held against vibration and supports two spaced-parallel platelike bearing members 12, 13. A shaft 14(corresponding to the shaft 1 of FIG. 1) is journaled, in antifriction bearings 15, 16 which are respectively mounted in the bearing members 12, 13. The shaft 14 is provided with a hub 17 which is rigid with a shutter blade 18. The hub 17 is further rigid with the housing 19 of a spring motor forming part of an auxiliary drive for the shutter blade 18' and further including a core 22 and a convoluted spring 26. Still further, the shaft 14 supports a cam 20 which is rigid with an axially offset index member 21 having a notch 21a.

The core 22 of the spring motor is freely rotatable on the shaft 14 and is rigid with a worm wheel 23v which is in mesh with a worm 24. The latter is driven by an electric motor corresponding to the motor of FIG. 1 so as to maintain the spring 26 under certain stress. The ends of the spring 26 are connected to the core 22 and to the housing 19 so that this spring tends to bias the shaft 14 in a clockwise direction.

The bearing member 12 supports two holding or arresting electromagnets 27, 28 whose armatures are coupled to pawls 29, 30 by way of pull rods 27a, 28a. The pawls 28, 29 are located in the plane of the index member 21 and are respectively turnable on pivot pins 29a, 30a mounted on the bearing member 12. Springs, not shown, bias the pawls 29, 30 toward the index member 21.

The cam has two pairs of sets of cam faces 20a, 20b and 20c, 20d. The faces 20a, 20b are steeper than the faces 20c, 20d; they serve to effect'rapid movement of the shutter blade 18 to closed position. The output unit'of the structure shown in'FlGS. 3 m5 further comprises a roller follower 31 (which preferably constitutes the outer race of an antifriction bearing) mounted on an intermediate portion of a lever or arm 33 fulcrumed on the plate 11,.as at 32, and having its free end provided with a post 34 for one end of a helical contraction spring 35 corresponding to the spring 5 of FIG. 1. The other end 35a of the spring 35 is connected to a second post 36 on the support 11.

The light-admitting opening 11a of the shutter is provided in the support 11. The shutter blad 18 has a concave edge face 18a whose radius of curvature corresponds to the radius of the opening 11a. When the blade 18 assumes the first position shown in FIG. 4, its edge face 18a is adjacent to and does not overlie the opening 11a; however, when the blade 18 turns in a clockwise direction, it rapidly overlies a substantial part of the opening 110 to thus effect rapid closing of the shutter. It will be noted (see particularly FIG. 5) that the blade 18 can overlie the opening 110 toprevent entry of light even if it advances well beyond the position in which the edge face 180 has been moved away from registry with the opening. This is desirable for reasons which were explained in'connection with FIG. 1, i.e., that the blade 18 continues to prevent entry of light even if its edge face 18a moves beyond the position 18a indicated in FIG. 5 by a phantom line.

The operation of the apparatus shown in FIGS. 3-5 is clearly analogous to that of the previously described apparatus. FIG. 5 illustrates the apparatus in idle or starting position. The blade 18 overlies the opening 11a and prevents passage of light. The springs 26 and 35 store maximum amounts of energy. In order to start an exposure, the electromagnet 28 is energized and its annature attracts the pawl by way of the pull rod 28a so that the tang of the pawl 30 leaves the notch 21a of the index member 21 and permits the cam 20 to turn in a clockwise direction-The roller follower 31 engages the peripheral surface of the cam 20 and begins to roll along the face 200 as soon as the pawl 30 is disengaged from the index member 21. The shutter 18 moves beyond the opening 11a and permits entry of light. This is due to the fact that the cam 20 and blade 18 are rigid with the hub 17 which in turn is rigid with the shaft 14. When the roller follower 31 reaches the deepmost portion of the recess flanked by cam faces 20c, 20d, the blade 18 rotates at a maximum speed and is thereupon decelerated while the roller follower 31 climbs by rolling along the face 20d. The kinetic energy of moving parts is almost consumed when the roller follower 31 reaches the peripheral surface 20a of the cam 20. In other words, the cam creeps" or moves rather slowly when the notch'21a of the index member 21 approaches and ultimately reaches the tang of the pawl 29. This position of the shutter blade 18 is shown in FIG. 4. The blade 18 then allows a maximum amount of light to pass through the opening 11a of the support 11.

When the apparatus should terminate the exposure, the electromagnet 27 is energized to attract the pawl 29 by way of its armature and pull rod 27a so that the tang of the pawl 29 leaves the notch 21a of the index member 21. The spring 35, assisted by the spring 26 of the spring motor, turns the cam 20 in a clockwise direction whereby the the roller follower 31 begins to roll along the steep face 20a of the cam 20 and accelerates the cam to a very high speed in order to insure rapid closing of the opening ll-a. Such rapid closing is further enhanced by the particular configuration of the edge face 18a on the shutter blade 18. The follower 31 rolls along and intermediate portion of the cam face 20b when the blade 18 closes the opening 11a but the inertia of moving parts, assisted by the spring 26, causes the cam 20 to continue to rotate in a clockwise direction and to return the position of FIG. 5 in which the tang of the pawl 30 enters the notch 21a. This completes the exposure and the apparatus is ready to make a fresh exposure as soon as the electromagnet 28 is energized to disengage the pawl 30 from the index member 21.

The spring 35 constitutes but one of several biasing means which can store and dissipate energy in response to movement of an output unit from a first to a second position. For example, the spring 35(or 5) can be replaced by a weight which descends by gravity during a first phase of rotation of the shutter blade and moves back to a higher level during the next-following phase to thereby respectively accelerate and decelerate the blade.

It is also possible to replace the auxiliary drive of FIGS. 3- 5 with other types of drives. For example, the shaft 14 can receive torque from a contactless magnetic clutch or it can be rigidly connected with the rotor of a suitable motor so that the spring motor and worm drive of FIG. 3 can be dispensed with. The friction clutch 37 of FIG. 1 serves toterminate the driving connection between the motor 10 and worm 9b (or 24) when the torsion spring 9 (or 26) stores a certain amount of energy. This friction clutch renders it possible to utilize a continuously operated motor 10 because it prevents excessive tensioning of the spring 9 (or 26). If it is desired to utilize an intermittently operated motor, the spring 9 or 26 can actuate a switch .(not shown) which opens the motor circuit as soon as the spring stores a predetermined amount of energy, namely, an amount which suffices to compensate for frictional losses, losses due to hysteresis, and for the fact that the cam 2 of FIG. 1 must move the follower 3 to the position 3".

An important advantage of the apparatus shown in FIGS. 1 and 3-5 is that the wear on the components of the output unit is negligible and that the apparatus must receive minimal amounts of energy. Such energy issupplied by the motor which stresses the spring 9 or 26.

When the apparatus of the present invention is utilized in a color printer, the carrier or index wheel 38 of the output unit (FIG. 6) carries three angularly spaced color filters 38b, 38c, 38d and an opaque mask 38a. Each filter permits passage of light in one of three additive-primary colors. The peripheral surface of the index wheel 38 is provided with four notches 38e, 38f, 38g, 38h which are respectively adjacent to the mask 38a and filters 38b-38d. The tang of a pawl 107a extends into the notch 38g under the bias of a torsion spring 140 to maintain the mask 38a in registry with a light-admitting opening (not shown). The pawl 107a constitutes the armature of an arresting or holding electromagnet 107 which is operatively connected to the exposure control of the printer. The index wheel 38 is rotatable on a shaft 101 and is rigid with a cam 39 having four pairs of cam faces or flanks 39a-39b, 39c39d, 39e- --39f, 39g-39h, one pair for each ofthe members 38a-38d. The recesses defined by the aforementioned pairs of cam faces on the cam 39 are equidistant from each other as considered on the circumferential direction of the cam. The remaining element of the output unit, the biasing means and the auxiliary drive for the cam 39 are identical with those shown in FIG. 1 and are denoted by similar numerals plus 100.

The operation is as follows:

At the start of a copying or printing cycle, the parts assume the positions shown in FIG. 6. The mask 38a overlies the lightadmitting opening of the printer and the pawl 107a extends into the notch 38g. The roller follower 103 engages the outermost part of the cam face 39d and the spring 105 stores a little less than a maximum amount of energy. The spring 109 also stores energy. When the exposure control of the printer sends a signal, the electromagnet 107 is energized and attracts the pawl 107a so that the cam 39 rotates in a clockwise direction under the action of springs 105, 109 until the pawl 107a enters the notch 38f. The filter 38d then registers with the light-admitting opening. The energization of the electromagnet 107 is of short duration because the springs 105, 109 can rotate the cam 39 and index wheel 38 even if the tang of the pawl 107a bears against the peripheral surface of the index wheel between the notches 38g, 38f.

The filter 38d dwells in registry with the light-admitting opening of the pointer until the exposure control energizes the electromagnet 107 for the second time whereby the cam 39 turns in a clockwise direction to move the filter 380 into registry with the opening. Movement of the filter 38d away from registry with the opening takes place very'rapidly for reasons which were outlined in connection with FIG. 1, i.e., due to specific configuration of the cam face 39b the other end of which is engaged by the follower 103 when the filter 38d registers with the opening. The same procedure is repeated two more times in order to move the filter 38b into registry with the opening and to finally return the mask 38a into the position of FIG. 6.

It will be seen that the apparatus of the present invention can move single movable part (blade'18) or a plurality of movable parts (mask 38a and filters 38b-38d) depending upon whether the apparatus is used in a camera, in a'blackand-white printer or in a color printer. It is further clear that the apparatus can transmit motion to two or more shutter blades, to a single filter, or to a plurality of filters whose number exceeds three. Still further, the apparatus of FIG. 6 can be replaced by three apparatuses of the type shown in FIGS. 3-5 whereby each such apparatus transmits motion to one of three color filters. A printer which can utilize the apparatus of FIG. 6 is disclosed, for example, in German Pat. No. 972,204. An important advantage of this apparatus is that a single electromagnet (107) suffices to effect movement'of several filters into operative position.

FIG. 7 illustrates a further apparatus which utilizes a modified output unit comprising a crank chain which includes an index wheel 41. The output unit also includes a gear train which transmits motion from the index wheel 41 to a rotary carrier member 47. The crank chain comprises a first link 42 one end of which is turnable on a fixed pin and the other end of which is coupled to a second link 43 and to one end of a helical contraction spring 44. The index wheel 41 constitutes a third link of the crank chain and has an eccentric pin 41b which is coupled to the link 43. The spring 44 tends to turn the index wheel 41 in a counterclockwise direction; the latter is provided with a notch 41a which can receive the tang of a pawl 52 constituting the armature of an arresting or holding electromagnet 51. The pawl 52 is biased by a torsion spring 53.

The carrier 47 is a disc and is provided with two circular filters 47a, 47b located diametrically opposite each other. The numeral 48 denotes a light-admitting opening which can register with the filter 470 or 47b in two predetermined angular positions of the carrier 47. The aforementioned gear train comprises a smaller gear 45 on the shaft of the index wheel 41 and a larger gear 46 on the shaft of the carrier 47. The ration of the gear train 45, 46 is 2:l i.e., the index wheel 41 completes two full revolutions in response to a single revolution of the carrier 47. The auxiliary drive of the apparatus shown in FIG. 7 comprises anelectric motor 50 which drives a I,

and tends to rotate the index wheel in a counterclockwise direction. The filter 47a is a yellow filter and the filter 47b is a blue filter; these filters can be utilized in a printer of the type disclosed in the copending U.S. Pat. application Ser. No. 714,188 filed Mar. 19, 1968 by Burger et al. and assigned to the same assignee.

When the electromagnet 51 is energized, the springs 44, 49 rotate the index wheel 41 in a counterclockwise direction and the electromagnet is deenergized before the wheel 41 completes a full revolution so that the pawl 52 can reenter the notch 41a in order to arrest the index wheel. The index wheel 41 and carrier 47 rotate at a maximum speed when the link 43 extends diametrically of the axis of the index wheel. As the latter continues to rotate in a counterclockwise direction, the spring 44 begins to store energy and stores a maximum amount of energy when-the pin 41b reaches the position 41b. Shortly, thereafter, the pin 41b returns to the position of FIG. 7 and the pawl 52 reenters the notch 41a, The filter 470 then assumes the position previously occupied by filter 47b because the angular displacement of the carrier 47 in response to a full revolution of the index wheel 4] equals The carrier 47 rotates in a clockwise direction. 1

The apparatus of FIG. 7 is particularly useful when the biasing means 44 must transmit motion to relatively heavy or bulky moving parts. It can also be used to transmit motion to the paper transporting or like assemblies of copying machines.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

l'claim:

1. Apparatus for transmitting motion to shutter blades, filters or analogous movable parts, comprising output means including cam means, a rotary shaft connected to said cam means, follower means, and lever means pivotable about a predetermined axis and supporting said follower means, said cam means being movable in synchronism with at least one movable part from a first to a second position, biasing means comprising resilient means connected to said lever means for biasing said follower means into engagement with said cam means, said cam means constituting means for transmitting energy between said resilient means and the one movable part and said resilient means being arranged to be stressed and to store a predetermined amount of energy in the first position of saidcam means, to accelerate said cam means during a first stage of movement from said first position with attendant dissipation of said energy, and to store energy during the nextfollowing state of movement of said cam means from first position with attendant deceleration of said cam means, said output means encountering at least some friction during movement of said cam means between said first and second positions', and auxiliary drive means for urging said cam means toward said second position with a force which suffices to at least compensate for said friction.

2. Apparatus as defined in claim 1, wherein said auxiliary drive means comprises spring means operatively connected with said cam means and means for'tensioning said spring means.

3. Apparatus as defined in claim 2, wherein said spring means comprises a torsion spring and wherein said cam means is operatively connected to one end of said torsion spring, said tensioning means comprising motor means having a rotary portion operatively connected to the other end of said torsion spring.

4. Apparatus as defined in claim 3, further comprising a transmission interposed between said motor means and said spring.

5. Apparatus as defined in claim 2, wherein said tensioning means comprises motor means arranged to store in said spring means energy which is just sufficient to compensate for said friction.

6. Apparatus as defined in claim 2, wherein said auxiliary drive means further comprises friction clutch means interposed between said spring means and said tensioning means.

7. Apparatus as defined in claim 1, further comprising arresting means for releasably holding said cam means in said first and second position.

8. Apparatus as defined in claim 7, wherein said arresting means comprises electromagnet means.

9. Apparatus as defined in claim 8, wherein said cam means has at least one notch and said arresting means comprises a pair of electromagnets one of which has a portion entering said notch in the first position and the other of which has a portion entering said notch in the second position of said cam means.

10. Apparatus as defined in claim 1, wherein said cam means has two sets of cam faces and said follower means is arranged to track said cam faces, the configuration of said cam faces being such that said resilient means dissipates energy to accelerate said cam means while said follower means one face and that said resilient means stores energy while said follower means tracks the other face of the respective set.

11. Apparatus as defined in claim 10, wherein the configuration of said one face in one to said sets is such that said cam means is accelerated to a greater speed than while said follower means tracks said one face of the other set.

12. Apparatus as defined in claim 1, wherein said cam means has at least one set of cam faces and said output means further comprises rotary index means coaxial with said cam means and provided with at least one peripheral notch angularly offset with reference to said cam faces, said follower means being arranged to track said cam faces and to thereby accelerate said cam means and said index means during movement of said cam means form said first position, and further comprising arresting means having a portion arranged to enter said notch in at least one position of said cam means.

13 Apparatus as defined in claim 12, wherein said follower means engages a radially outermost portion of one of said faces in the first position of said cam means.

14 Apparatus as defined in claim 1, wherein said output means further comprises carrier means and said movable parts include a plurality of color filters supported by said carrier means.

15. Apparatus as defined in claim 14, wherein said further comprising arresting means for holding said carrier means against the action of said resilient means and said auxiliary drive means in several angularly spaced positions in each of which one ofsaid filters assumes a predetermined position. 

